I have to agree with ScienceDoc.
Living in Switzerland with only the occasional need for a car, I signed up with the Swiss service "Mobility" which has hundreds of cars available all over the country for as little as Sfr2 (about US$1.38) per hour. Obviously for that you don't get much of a car, but the likes of Audi's and Volkwagen's are available if required too.
The prime intention is to increase the use of our excellent rail services and keep the highways relatively clear which is obviously working. The majority of the Mobility cars are available at railway stations and are activated with a personal smartcard. The receiver in the car is activated via satelitte from central control in, I think, Berne ensuring your reserved car is available to you at the time of booking.
Excellent system and very popular here.
Whooaahh!!!